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-<refentry id="vidioc-g-selection">
-
- <refmeta>
- <refentrytitle>ioctl VIDIOC_G_SELECTION, VIDIOC_S_SELECTION</refentrytitle>
- &manvol;
- </refmeta>
-
- <refnamediv>
- <refname>VIDIOC_G_SELECTION</refname>
- <refname>VIDIOC_S_SELECTION</refname>
- <refpurpose>Get or set one of the selection rectangles</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcprototype>
- <funcdef>int <function>ioctl</function></funcdef>
- <paramdef>int <parameter>fd</parameter></paramdef>
- <paramdef>int <parameter>request</parameter></paramdef>
- <paramdef>struct v4l2_selection *<parameter>argp</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Arguments</title>
-
- <variablelist>
- <varlistentry>
- <term><parameter>fd</parameter></term>
- <listitem>
- <para>&fd;</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>request</parameter></term>
- <listitem>
- <para>VIDIOC_G_SELECTION, VIDIOC_S_SELECTION</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>argp</parameter></term>
- <listitem>
- <para></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-
- <refsect1>
- <title>Description</title>
-
- <note>
- <title>Experimental</title>
- <para>This is an <link linkend="experimental"> experimental </link>
- interface and may change in the future.</para>
- </note>
-
- <para>The ioctls are used to query and configure selection rectangles.</para>
-
-<para> To query the cropping (composing) rectangle set &v4l2-selection;
-<structfield> type </structfield> field to the respective buffer type.
-Do not use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE
-</constant> instead of <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
-</constant>. Use <constant> V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> instead of
-<constant> V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE </constant>. The next step is
-setting the value of &v4l2-selection; <structfield>target</structfield> field
-to <constant> V4L2_SEL_TGT_CROP_ACTIVE </constant> (<constant>
-V4L2_SEL_TGT_COMPOSE_ACTIVE </constant>). Please refer to table <xref
-linkend="v4l2-sel-target" /> or <xref linkend="selection-api" /> for additional
-targets. The <structfield>flags</structfield> and <structfield>reserved
-</structfield> fields of &v4l2-selection; are ignored and they must be filled
-with zeros. The driver fills the rest of the structure or
-returns &EINVAL; if incorrect buffer type or target was used. If cropping
-(composing) is not supported then the active rectangle is not mutable and it is
-always equal to the bounds rectangle. Finally, the &v4l2-rect;
-<structfield>r</structfield> rectangle is filled with the current cropping
-(composing) coordinates. The coordinates are expressed in driver-dependent
-units. The only exception are rectangles for images in raw formats, whose
-coordinates are always expressed in pixels. </para>
-
-<para> To change the cropping (composing) rectangle set the &v4l2-selection;
-<structfield>type</structfield> field to the respective buffer type. Do not
-use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE
-</constant> instead of <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
-</constant>. Use <constant> V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> instead of
-<constant> V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE </constant>. The next step is
-setting the value of &v4l2-selection; <structfield>target</structfield> to
-<constant>V4L2_SEL_TGT_CROP_ACTIVE</constant> (<constant>
-V4L2_SEL_TGT_COMPOSE_ACTIVE </constant>). Please refer to table <xref
-linkend="v4l2-sel-target" /> or <xref linkend="selection-api" /> for additional
-targets. The &v4l2-rect; <structfield>r</structfield> rectangle need to be
-set to the desired active area. Field &v4l2-selection; <structfield> reserved
-</structfield> is ignored and must be filled with zeros. The driver may adjust
-coordinates of the requested rectangle. An application may
-introduce constraints to control rounding behaviour. The &v4l2-selection;
-<structfield>flags</structfield> field must be set to one of the following:
-
-<itemizedlist>
- <listitem>
-<para><constant>0</constant> - The driver can adjust the rectangle size freely
-and shall choose a crop/compose rectangle as close as possible to the requested
-one.</para>
- </listitem>
- <listitem>
-<para><constant>V4L2_SEL_FLAG_GE</constant> - The driver is not allowed to
-shrink the rectangle. The original rectangle must lay inside the adjusted
-one.</para>
- </listitem>
- <listitem>
-<para><constant>V4L2_SEL_FLAG_LE</constant> - The driver is not allowed to
-enlarge the rectangle. The adjusted rectangle must lay inside the original
-one.</para>
- </listitem>
- <listitem>
-<para><constant>V4L2_SEL_FLAG_GE | V4L2_SEL_FLAG_LE</constant> - The driver
-must choose the size exactly the same as in the requested rectangle.</para>
- </listitem>
-</itemizedlist>
-
-Please refer to <xref linkend="sel-const-adjust" />.
-
-</para>
-
-<para> The driver may have to adjusts the requested dimensions against hardware
-limits and other parts as the pipeline, i.e. the bounds given by the
-capture/output window or TV display. The closest possible values of horizontal
-and vertical offset and sizes are chosen according to following priority:
-
-<orderedlist>
- <listitem>
- <para>Satisfy constraints from &v4l2-selection; <structfield>flags</structfield>.</para>
- </listitem>
- <listitem>
- <para>Adjust width, height, left, and top to hardware limits and alignments.</para>
- </listitem>
- <listitem>
- <para>Keep center of adjusted rectangle as close as possible to the original one.</para>
- </listitem>
- <listitem>
- <para>Keep width and height as close as possible to original ones.</para>
- </listitem>
- <listitem>
- <para>Keep horizontal and vertical offset as close as possible to original ones.</para>
- </listitem>
-</orderedlist>
-
-On success the &v4l2-rect; <structfield>r</structfield> field contains
-the adjusted rectangle. When the parameters are unsuitable the application may
-modify the cropping (composing) or image parameters and repeat the cycle until
-satisfactory parameters have been negotiated. If constraints flags have to be
-violated at then ERANGE is returned. The error indicates that <emphasis> there
-exist no rectangle </emphasis> that satisfies the constraints.</para>
-
- </refsect1>
-
- <refsect1>
- <table frame="none" pgwide="1" id="v4l2-sel-target">
- <title>Selection targets.</title>
- <tgroup cols="3">
- &cs-def;
- <tbody valign="top">
- <row>
- <entry><constant>V4L2_SEL_TGT_CROP_ACTIVE</constant></entry>
- <entry>0x0000</entry>
- <entry>The area that is currently cropped by hardware.</entry>
- </row>
- <row>
- <entry><constant>V4L2_SEL_TGT_CROP_DEFAULT</constant></entry>
- <entry>0x0001</entry>
- <entry>Suggested cropping rectangle that covers the "whole picture".</entry>
- </row>
- <row>
- <entry><constant>V4L2_SEL_TGT_CROP_BOUNDS</constant></entry>
- <entry>0x0002</entry>
- <entry>Limits for the cropping rectangle.</entry>
- </row>
- <row>
- <entry><constant>V4L2_SEL_TGT_COMPOSE_ACTIVE</constant></entry>
- <entry>0x0100</entry>
- <entry>The area to which data is composed by hardware.</entry>
- </row>
- <row>
- <entry><constant>V4L2_SEL_TGT_COMPOSE_DEFAULT</constant></entry>
- <entry>0x0101</entry>
- <entry>Suggested composing rectangle that covers the "whole picture".</entry>
- </row>
- <row>
- <entry><constant>V4L2_SEL_TGT_COMPOSE_BOUNDS</constant></entry>
- <entry>0x0102</entry>
- <entry>Limits for the composing rectangle.</entry>
- </row>
- <row>
- <entry><constant>V4L2_SEL_TGT_COMPOSE_PADDED</constant></entry>
- <entry>0x0103</entry>
- <entry>The active area and all padding pixels that are inserted or modified by hardware.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </refsect1>
-
- <refsect1>
- <table frame="none" pgwide="1" id="v4l2-sel-flags">
- <title>Selection constraint flags</title>
- <tgroup cols="3">
- &cs-def;
- <tbody valign="top">
- <row>
- <entry><constant>V4L2_SEL_FLAG_GE</constant></entry>
- <entry>0x00000001</entry>
- <entry>Indicates that the adjusted rectangle must contain the original
- &v4l2-selection; <structfield>r</structfield> rectangle.</entry>
- </row>
- <row>
- <entry><constant>V4L2_SEL_FLAG_LE</constant></entry>
- <entry>0x00000002</entry>
- <entry>Indicates that the adjusted rectangle must be inside the original
- &v4l2-rect; <structfield>r</structfield> rectangle.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </refsect1>
-
- <section>
- <figure id="sel-const-adjust">
- <title>Size adjustments with constraint flags.</title>
- <mediaobject>
- <imageobject>
- <imagedata fileref="constraints.png" format="PNG" />
- </imageobject>
- <textobject>
- <phrase>Behaviour of rectangle adjustment for different constraint
- flags.</phrase>
- </textobject>
- </mediaobject>
- </figure>
- </section>
-
- <refsect1>
- <table pgwide="1" frame="none" id="v4l2-selection">
- <title>struct <structname>v4l2_selection</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>type</structfield></entry>
- <entry>Type of the buffer (from &v4l2-buf-type;).</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>target</structfield></entry>
- <entry>Used to select between <link linkend="v4l2-sel-target"> cropping
- and composing rectangles</link>.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>flags</structfield></entry>
- <entry>Flags controlling the selection rectangle adjustments, refer to
- <link linkend="v4l2-sel-flags">selection flags</link>.</entry>
- </row>
- <row>
- <entry>&v4l2-rect;</entry>
- <entry><structfield>r</structfield></entry>
- <entry>The selection rectangle.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>reserved[9]</structfield></entry>
- <entry>Reserved fields for future use.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </refsect1>
-
- <refsect1>
- &return-value;
- <variablelist>
- <varlistentry>
- <term><errorcode>EINVAL</errorcode></term>
- <listitem>
- <para>Given buffer type <structfield>type</structfield> or
-the selection target <structfield>target</structfield> is not supported,
-or the <structfield>flags</structfield> argument is not valid.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><errorcode>ERANGE</errorcode></term>
- <listitem>
- <para>It is not possible to adjust &v4l2-rect; <structfield>
-r</structfield> rectangle to satisfy all contraints given in the
-<structfield>flags</structfield> argument.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><errorcode>EBUSY</errorcode></term>
- <listitem>
- <para>It is not possible to apply change of the selection rectangle
-at the moment. Usually because streaming is in progress.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-
-</refentry>